Systems for automatically controlling the manner in which a pattern is to be sewn on a workpiece have been heretofore used widely in the garment and shoe industries. Such systems were at one time largely mechanical in nature and included various mechanical memory elements which would dictate the pattern of movement of the workpiece. These systems have been replaced to a large extent by digital control logic which utilizes a digital storage device for the purpose of dictating the pattern of movement. These digital storage devices can include among other things: a paper tape, a magnetic tape, or an electronic memory such as a read only memory or a programmable read only memory otherwise known as a ROM or PROM. The pattern of movement which is usually stored in these various storage devices is sequentially accessed by the digital control logic in such a manner as to control the movement of the workpiece relative to the sewing head.
It is to be appreciated that the patterns of movement which are thus stored within the digital storage device may require a considerable amount of storage space. In addition, the digital storage device may also be required to store information other than that specifically relating to the controlled movement of the workpiece. In this regard, the digital storage device may contain information relating to stitching parameters. This results in a considerable demand being placed upon the limited storage space within the given storage element.
It is also to be appreciated that provision must be made for securely holding the workpiece when the same is being moved by the digital control logic pursuant to the reading of a particular stored pattern of movement. In this regard, most automatic sewing machines include a clamping mechanism which holds the workpiece during the entire automatic sewing operation. These clamping mechanisms are usually configured for the particular sewing pattern which is to be sewn. This requires an individual clamping mechanism for each and every sewing pattern that is to be automatically sewn.
Clamping mechanisms moreover do not provide for an expeditious unloading of the workpiece when the same has been completely stitched. In this regard, the necessity for securely clamping the workpiece during the sewing operation is considered more important than the need to provide a mechanism for quickly ejecting the completed workpiece.